Drug tests

Back when physicians relied on a huge gamma counter to measure the hormone level in a test sample, it seemed silly to think about a day when a small drug test kit could detect evidence of drug use. Today what once seemed like an impossible dream has become a reality. Now law enforcement officers and employers both turn the drug test kit for evidence of recent drug use. Looking at such tiny kits, it is difficult to appreciate the degree to which the science for such a kit has copied the science that was used back when physicians counted on data from the huge gamma counters.

Back before the development of a drug test kit, the medical community had begun to understand how competition could be used in a testing situation. More than 35 years ago, when physicians counted on radioimmunoassay (RIA) to measure the level of certain hormones in the bloodstream of their patients, the medical community had initiated a reliance on the competition between molecules. Then the competing molecules included both a natural hormone labeled with a radioactive substance and an unlabelled conjugate.

In the process of conducting those old RIA tests, the laboratory doctor would count on the labeled hormone in the test sample to search out the antibody in the testing device, typically a test tube. The labeled hormone would bind to that antibody. After the antibodies had been exposed to the sample, then the doctor would plan to add the unlabelled conjugate. The conjugate would bind to the antibodies that had not bound to the labeled hormone, the hormone in the test sample.

The testing device would measure the amount of radioactivity emitted by each test tube. At that time the doctor did not use a drug test kit. At that time the doctor ran the test tubes with the test samples through a large machine that could detect radioactive particles. The doctor could not test for more than one hormone at a time. The doctor then could not plan to conduct a panel of tests, as test-givers now do with a drug test kit.

At the present time, a test-giver selects the drug test kit that will allow detection of the drugs that an employer or a law enforcement officer think a test subject has used. Sometimes the test-giver uses only a 3 panel test. That would allow the detection of marijuana, cocaine and methamphetamine. When the test –giver suspects the use of other drugs, then that test-giver selects a different sort of drug test kit.

For example, the test-giver might decide to use a 4-panel drug test kit. Such a kit would allow the test-giver to detect recent use of opiates, in addition to use of marijuana, cocaine and methamphetamine. If the test giver were to suspect use of an amphetamine, then that test giver might choose to use a 5-panel drug test kit. The 5-panel kit could detect traces of 2 different amphetamines, traces of PCP, traces of marijuana and traces of cocaine.

All of the kits use competition for a binding site to pick-up the presence of a drug. The drug combines with a protein conjugate. It competes for that site with a recombined drug that is present in the drug test kit. If the drug “wins” that competition, then the test-giver will have evidence of recent drug use by the test subject.